Oral Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

Evaluation of bone microstructure of distal radius and distal tibia on human objects using phase-contrast synchrotron radiation computed tomography (#23)

Ali Ghasem-Zadeh 1 , Rachel Davey 2 , Michele Clarke 3 , Cat Shore-Lorenti 4 , Simon Murray 5 , Duncan Butler 6 , Chris Hall 6 , Peter Ebeling 4 , Jeffrey Zajac 1 , Ego Seeman 1
  1. Departments of Endocrinology and Medicine , Austin Health, the University of Melbourne, Heidelberg, VIC, Australia
  2. Department of Medicine, Austin Health, the University of Melbourne, Heidelberg, VIC, Australia
  3. University of Melbourne, Melbourne, VIC, Australia
  4. Department of Medicine, School of Clinical Sciences at Monash Health, Monash University, Clayton, VIC, Australia
  5. Departments of Anatomy, University of Melbourne, Melbourne, VIC, Australia
  6. Australian Synchrotron Radiation, ., Clayton, VIC, Australia

Introduction

There are challenges in accurately determining cortical porosity using High-Resolution peripheral Quantitative Computed Tomography (HR-pQCT) due to issues in image resolution, segmentation, beam hardening associated with poly-energic photons and blurred interface edges produced by larger point spread function.  These issues are critical because porosity reduces bending strength disproportionate to the bone loss producing it so that errors in quantification underestimate fracture risk and fail to identify persons at risk of fragility fracture (Zebaze et al 2010).  

During radiation transmission of x-ray photons, regardless of the attenuation, photons undergo small phase shifts, which can be converted into changes in amplitude, and observed as in images with different contrast.  Australian Synchrotron Radiation provides computed tomographic images, 9.6-micron voxel size, using monochromatic and parallel x-ray photons.  We hypothesised that HR-pQCT images used to measure cortical porosity produced by Haversian canal cross-sections and small pores produced by osteocytic lacunae would be quantifiable despite the relatively lower resolution of the HR-pQCT images.  We compared the bone microstructural indices using Synchrotron Radiation photon attenuation and phase contrast-based computed tomography images versus images obtained using HR-pQCT.

 Methods

Thirty-two post-mortem human radii and tibiae, fresh and dry specimens, were imaged at the Australian Synchrotron Radiation-Imaging and Medical Beamline (IMBL), using 60kV monochromatic x-ray based tomography. Silicon amorphous detectors with voxel sizes of 9.6 and 14.6 microns have been used to create x-ray photons attenuation and phase-contrast based tomographic images.

 Results

The preliminary comparison of axial images has shown higher visibility for small pores and Haversian canals in the phase contrast-based images. 

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Conclusion

We infer that the accuracy of distal radial and distal tibial cortical porosity using HR-pQCT can be validated using synchrotron imaging as a referent gold standard.